Carsharing systems are gaining new members every month. However, few studies formally define the system and illustrate the systematic processing of administrative data sets to estimate indicators regarding both demand and supply objects. The first outcome of this research is the definition of the object model for a carsharing system. Rich transaction data sets, generally used for the production of monthly bills, are used to estimate indicators describing how the carsharing system is used in the Montreal area of Quebec, Canada. Indicators describing the main objects of the system-members, trip chains (transactions), cars, and stations-are estimated by using continuous data. The demand object analysis focuses on the study of members and their trip chains using the shared cars. The analysis shows that carsharing members are younger than the overall population, with an overrepresentation of 25- to 39-year-olds. The persistency of active members within the carsharing system is estimated at around 60% after 4 months and 50% after 12 months. The supply-objects analysis focuses on the study of cars and stations. Spatial dispersion of members with respect to stations used and typical use of cars is illustrated over long periods. With the increase in the number of members, transactions, cars, and stations, carsharing organizations need to find new ways to manage growth and optimize their networks. A clearer understanding of how their systems are used will help them develop enhanced planning and modeling abilities.